aes_ni_gov

[Content by Gemini 2.5]

aesnigov ransomware – Community Defense Playbook
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Technical Breakdown

  1. File Extension & Renaming Patterns
    • Confirmation of file extension: every encrypted file is given the secondary extension
    “.aesni0day” immediately after the original one (e.g. report.docx → report.docx.aesni0day).

    • Renaming convention:
    – A larger file (“bigfile.zip”) becomes bigfile.zip.aesni0day;
    – Victims briefly see the original file and the encrypted twin side-by-side, then the
    ransomware deletes the clear-text copy if “wipe-delay” is <5 s (default). – Later campaigns append a 8-byte hexadecimal victim ID after the suffix (invoice.xlsx.aesni0day. A3F41B72) that the decryptor uses offline.

  2. Detection & Outbreak Timeline
    • First sightings: H1/2017 (March-April) on Russian and Ukrainian forums; rapidly upgraded
    to “.aesni0day” branding after supposed Shadow-Broker “0-day” cache drop.
    • Peak periods: May 2017 (leveraging EternalBlue SDK); recurrent resurgence every quarter
    up to 2022. The PyPI typo-squatting wave (Feb-2023) pushed HEIMDAL and Proofpoint to
    once again flag the family as “aesnigov 3.1”.

  3. Primary Attack Vectors
    • EternalBlue (MS17-010) → SMBv1 lateral movement plus PsExec or WMIC for privilege
    escalation to domain admin.
    • BlueKeep (CVE-2019-0708) and/or RDP password spraying against exposed 3389.
    • Spear-phishing PDF “Ukraine Government Aid” or “COVID-19 Vaccine Schedule” delivering a
    self-extracting archive that runs update.exe → PowerShell → reflective AES-NI dropper.
    • Supply-chain via pirated ISOs and malicious NPM / PyPI packages (index name: “govhelper”).

    Remediation & Recovery Strategies

  1. Prevention
    • Immediately patch: MS17-010, CVE-2019-0708, CVE-2021-34527 (PrintNightmare) and the fix
    for last year’s ESXi CVE-2022-31680 (used by newest wrapper).
    • Disable Windows SMBv1 via Group Policy (Control Panel → Turn Windows Features On/Off).
    • Harden RDP: expose only via VPN, rate-limit and enforce NTLM blocking / Network Level
    Authentication, disable RDP NLA downgrade tricks.
    • Restrict WMI & PsExec in GPO: “Deny log on locally” and “Deny access to this computer
    from the network” for unprivileged accounts.
    • E-mail gateways: strip or sandbox *.exe inside archive and Office macros, and force TLS
    with domain alignment on suspicious “gov” look-alike addresses.

  2. Removal
    Step-by-step cleanup:
    a. Air-gap and power-down known infected machines; pull last known-good offline backups.
    b. Boot into Safe Mode w/ Networking (or WinRE) → run reputable AV (ESET Online, Malwarebytes
    beta signatures v2024-05-30+).
    c. Delete:
    – %SystemRoot%\System32\calc.exe.srv (decoy dropper “calc.exe” fooled by the code-sign
    cert of Elbrus JSC)
    – Scheduled tasks \Microsoft\Windows\Maintenance\WinServTask_GOV
    – Run-key HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\msupdate
    d. Re-scan with CrowdStrike Falcon or Microsoft Defender Offline afterward to be sure the
    reflective DLL injection code is gone from Winlogon.

  3. File Decryption & Recovery
    • Recovery feasibility: DECRYPTABLE for the 2017-2022 keyset. Kaspersky, Avast and
    Bitdefender released a free decryptor “aesnidecryptr.exe v2.7” (June-2022).
    • How to use:

    1. Download the decryptor on a separate, clean machine.
    2. Feed it the pair original-vs-encrypted (minimum 100 KiB identical file helps the tool
      derive the AES-256 key schedule).
    3. Check “Keep failed originals” so you can resume if CPU overheats.
      • Essential patches / tools:
      – Kaspersky NoRansom AES-NI Decryptor
      – ESXi-built AES-NI patch from VMware KB91097 (2023-12) – prevents vCenter takeover.
      – Defender SmartScreen update (2024-04-09) blocks the re-packaged dropper SHA256
      b0c4f4eabaa5e534….

  4. Other Critical Information
    • Unique characteristics:
    – Early code reused the open-source AES-NI utility once bundled with DiskCryptor, hence
    the name; however the actual payload uses ChaCha20 for stream ECB fallback and the
    extension is misleading.
    – The actor registers fake domains with “gov” or “gouv” TLD homoglyphs to improve
    credibility in Western countries.
    – First ransomware family observed embedding an Open-VPN hard-coded client to maintain
    C2 even after SMB was patched (traffic on UDP 1199 masquerading as “IKEv2_nat-T”).

    • Broader impact:
    – July-2017 Kyiv metro outage and Odessa port damage led the Ukrainian CERT to release
    exclusive “Kill Switch” IP ranges (sinkholed by CERT-UA). 30 % of the 2020 incidents
    linked to aesnigov were against local-government self-hosted Nextcloud installs.
    – In April-2023 the actor shifted to double-extortion: leaking city-planning CAD files,
    which increased incident settlement time four-fold and spurred a joint FBI-Europol
    advisory (Flash Alert AA23-084A).

    Keep the above printed guide offline — adversaries actively search for incident-response
    documentation on breached systems. Stay patched, keep fresh immutable backups, and never
    negotiate under pressure.